1、Lessons Learned Entry: 0349Lesson Info:a71 Lesson Number: 0349a71 Lesson Date: 1994-10-26a71 Submitting Organization: JPLa71 Submitted by: J.F. ClawsonSubject: Magellan (MGN) High Rocket Engine Module (REM) Temperatures Abstract: Early in the flight, Magellan REM temperatures exceeded predictions by
2、 over 20 degrees C. for certain spacecraft orientations. This necessitated changes in the mission profile. Subsystem thermal design modifications had been made based solely on analysis and implemented without any test verification. Design changes should be verified by test. The prime contractor shou
3、ld be responsible for thermal integration of the REM. The REM should be subjected to a series of solar thermal vacuum orientations at the subsystem level.Description of Driving Event: Early in the MGN flight, REM temperatures exceeded predictions by over 20 degrees C. for selected ranges of spacecra
4、ft orientations.During the MGN System Thermal Vacuum Test (STV) in July 1988, the REM exhibited a similar problem in that temperatures were about 25 degrees C. warmer than expected. There were no REM subsystem solar thermal vacuum tests conducted prior to the STV. Since the only solar thermal vacuum
5、 test was conducted at the system level, attainable REM orientations during that test were restricted. Following the STV, modifications based solely on analyses by the REM supplier were implemented without any test verification.Current thinking (based on flight data) is that in addition to nozzle en
6、trapment of solar energy, the thermal model was too simplified; and the thermal surface properties of the engines were different than originally thought.The REM high mission temperatures caused two major impacts: 1) the mission attitude profile had to be significantly modified to avoid overheating t
7、he REMS, which was a major constraint on mission Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-operations, 2) a major ground test program was required to demonstrate temperature capabilities above the original upper limits.Additional Keyword(s): De
8、sign Fix VerificationReference(s): PFR #52226 (ISA #5069), PFR #52227 (ISA #5552)Lesson(s) Learned: 1. Subsystem thermal design modifications based solely on analysis and implemented without any test verification can result in unexpected system level constraints.2. System thermal integration analysi
9、s and testing can function as an independent verification of subsystem thermal design.Recommendation(s): 1. Thermally isolated subsystems with complex geometries such as the REM should be subjected to a series of solar thermal vacuum orientations at the subsystem level.2. Given the lack of a REM sub
10、system solar thermal vacuum test, the spacecraft system thermal vacuum test fixturing should allow much greater flexibility in orientation simulation.3. Design changes should be verified by test. Had a flight spare (or developmental) REM existed, such a retest would have easily shown that the proble
11、m was not solved.4. Thermal integration of the REM should be the responsibility of the prime contractor, not the REM supplier.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Test & VerificationProvided by IHSNo
12、t for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Approval Info: a71 Approval Date: 1993-01-29a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
